The Middle Indo-Aryan (MIA) stage in the evolution of Indo-Aryan languages is thought to have spanned more than a millennium between 600 BC - 1000 AD, and is often divided into three major subdivisions.

The middle stage is represented by the various literary Prakrits, especially Sauraseni, Maharashtri and Magadhi. The term Prakrit is also often applied to Middle Indo-Aryan languages (prakrita literally means "natural" as opposed to sanskrita, which literally means "constructed" or "refined"). Modern scholars such as Michael C. Shapiro follow this classification by including all Middle Indo-Aryan languages under the rubric of "Prakrits", while others emphasise the independent development of these languages, often separated from Sanskrit by social and geographic differences.[2]

The Indo-Aryan languages are commonly assigned to three major groups - Old Indo-Aryan languages, Middle Indo-Aryan languages and Early Modern and Modern Indo-Aryan languages, a linguistic and not strictly chronological classification.

The Middle Indo-Aryan languages are younger than Old Indo-Aryan languages such Rigvedic Sanskrit,[5] but were contemporaneous with the Classical Sanskrit, another Old Indo-Aryan language.[6]

Some scholars believe that a number of morphophonological and lexical features betray the fact that Middle Indo-Aryan languages are not direct continuations of Old Indo-Aryan languages (such as ṚgvedicSanskrit, the main base of Classical Sanskrit); rather they descend from dialects which, despite many similarities, were different from Ṛgvedic.[7]

MIA languages, though individually distinct, share features of phonology and morphology which characterize them as parallel descendants of Old Indo-Aryan. Various sound changes are typical of the MIA phonology:

all final consonants except '-ṃ' are dropped unless they are retained in 'sandhi' junctions.

The most conspicuous features of the morphological system of these languages are: loss of the dual; thematicization of consonantal stems; merger of the f. 'i-/u-' and 'ī-/ū-' in one 'ī-/ū-' inflexion, elimination of the dative, whose functions are taken over by the genitive, simultaneous use of different case-endings in one paradigm; employment of 'mahyaṃ' and 'tubhyaṃ' as genitives and 'me' and 'te' as instrumentals; gradual disappearance of the middle voice; coexistence of historical and new verbal forms based on the present stem; and use of active endings for the passive. In the vocabulary, the MIA languages are mostly dependent on Old Indo-Aryan, with addition of a few so-called 'deśī' words of (often) uncertain origin.[8]

A Middle Indo-Aryan innovation are the serial verb constructions that have evolved into complex predicates in modern north Indian languages such as Hindi. For example भाग जा (bhāg jā) 'go run' means run away, पका ले (pakā le) 'take cook' means to cook for oneself, and पका दे (pakā de) 'give cook' means to cook for someone. The second verb restricts the meaning of the main verb or adds a shade of meaning to it.[4] Subsequently the second verb was grammaticalised further into what is known as a light verb, mainly used to convey lexical aspect distinctions for the main verb.

Pali is the best attested of the Middle Indo-Aryan languages because of the extensive writings of early Buddhists. These include canonical texts, canonical developments such as Abhidhamma, and a thriving commentarial tradition associated with figures such as Buddhaghosa. Early Pāli texts, such as the Sutta-nipāta contain many "Magadhisms" (such as heke for eke; or masculine nominative singular in -e). Pāli continued to be a living second language until well into the second millennium. The Pali Text Society was founded in 1881 by T.W Rhys Davids to preserve, edit, and publish texts in Pāli, as well as English translations.

Many texts in Kharoṣṭhi script have been discovered in the area centred on the Khyber Pass in what was known in ancient times as Gandhara and the language of the texts came to be called Gāndhārī. These are largely Buddhist texts which parallel the Pāli Canon, but include Mahāyāna texts as well. The language is distinct from other MI dialects.

An apabhramsa (also: avahatta) was a language developed from Prakrits.[10][11][12] Modern Provincial languages developed from different apabhramsas. Patanjali was the first to use apabhramsa in his Mahabhasya (200 BC). The term is derived from the Sanskrit word Apabhrasta,[13] means a corrupted form of Sanskrit. Mostly Jain religious language and spiritual literature of Siddhas was composed in Apabhramsa language.
When the Romani people migrated from Rajasthan, Punjab, Sindh and Afghanistan in the 1st century AD, they were speaking an apabhramsa language pertaining to the Western part of India. They spread in Western countries around the 12th century AD.[14]

^"The most archaic Old Indo-Aryan is found in Hindu sacred texts called the Vedas, which date to approximately 1500 BCE". Encyclopedia Britannica - Indo-Aryan languages. General characteristics.

^"If in "Sanskrit" we include the Vedic language and all dialects of the Old Indian period, then it is true to say that all the Prakrits are derived from Sanskrit. If on the other hand " Sanskrit " is used more strictly of the Panini-Patanjali language or "Classical Sanskrit," then it is untrue to say that any Prakrit is derived from Sanskrit, except that S'auraseni, the Midland Prakrit, is derived from the Old Indian dialect". Introduction to Prakrit, by Alfred C Woolner. Baptist Mission Press 1917

^Oberlies, Thomas Pali: A Grammar of the Language of the Theravāda Tipiṭaka, Walter de Gruyter, 2001.